Alternation of Generation
Each generation of Fungi Kingdom is opposite of its parents generation. A generation of fungal cells can either diploid, with two copies of each chromosome, or haploid, with only one copy of each chromosome. Most fungi that you would recognize as fungi, for example mushrooms (club fungi), the fruiting bodies of sac fungi and molds that appear above ground, are diploid. On the other hand, haploid fungi make up the hyphae cells and underground mycelium before the mycelium undergoes sexual reproduction. For the most part, the underground hyphae-roots which often sustain fungi that grow above the ground are of a haploid generation while fungi that grow above the soil or on the sides of trees are of a diploid generation.
Each of the two generations of fungi undergoes a different type of reproduction. Haploids sexually reproduce, joining the two nuclei of two different strands of hyphae cells to produce a new strand of diploid hyphae cells which will the sprout into an above-earth mushroom (etc.) Diploids, on the other hand, produce special haploid cells using Mitosis to be released as spores into the ground. The children of diploids become haploid mycelium that will produce more diploids.
Three Types of Fungi Reproduction
There are five, debatably six, phylums of fungi (see evolution section): Conjunction, Club, Sac, Imperfect, primitive and, perhaps, lichen. Each phylum has its respective method of reproduction. In this section, we will cover the three most important types of Fungi Reproductions: that of Molds/Conjunction Fungi (Zygomycota), Club Fungi (Basidiomycota) and Sac Fungi (Ascomycota). Enjoy fungi sex!
Phylum Zygomycota: Molds (Conjunction Fungi)
Sexual Reproduction: (1) When two haploid strands of hyphae, one (+) and one (-), meet, they fuse at the edges and begin to form a multi-celled, thick-walled zygosporangium. (2) The nuclei from the opposite hyphal cells fuse together inside the zygosporangium, forming a diploid-celled zygospore. (3) The diploid zygospore grows upwards into the air by undergoing meiosis. This mold protrusion is called sporangium (haploid). (4) The sporangium releases haploid spores into the air. (5) A spore lands into its final destination (e.g. in the earth, in bread, etc.) and begins to undergo mitosis forming new mycelium.
Asexual Reproduction: (1) Haploid mycelium sprouts into haploid sporangium without ever creating a diploid zygospore. (2) Spores are released into the air; the spores begin to sprout mycelium when they land.
Phylum Basidiomycota: Club Fungi (Mushrooms)
Sexual Reproduction: (1) Two strands of haploid mycelium, one (+) and one (-), fuse to create a diploid mycelium strand that contains two nuclei in each of its adjoined hyphal cells. (2) When above earth environmental changes become favorable, a visible mushroom forms above the diploid hyphae. (3) On the gills of the mushroom, diploid basidia (which will form into spores) begin to form; each basidia cell contains two nuclei. (4) The two nuclei in the basidia cells fuse creating a – still diploid – basidium. (5) Each basidia cell then undergoes meiosis producing haploid nuclei that matures into basidiospores. (6) The basidiospores are dispersed; when they land in their final destination points, they germinate, forming haphae
Asexual Reproduction: Basidiomycota only EXTREMELY rarely ever asexually reproduces, so don’t sweat it!
Sexual Reproduction: Sac Fungi seldom reproduce sexually. (1) Two strands of haploid hyphae, one (+) and one (-), come in close contact: both form a haploid Ascogonium out of hyphae. The Ascogonium is a sac with many fungi cell nuclei compacted close. (2) Out of the Ascogonium, many strands of hyphae grow above earth. These filaments synthesize to form the structure of the “fruiting” body of the fungi. At the tip of the fruiting body, each hyphae strand forms into an ascus. Each ascus contains two nuclei. (3) The nuclei in the ascus fuse to create a diploid ascus. Then, each ascus undergoes meiosis, producing haploid nuclei. (4) The haploid nuclei undergo meiosis again, resulting in eight ascospores in each ascus. Each ascus bursts, releasing the ascospores into the air. (5) When an ascospore reaches its destination, hyphae develop and a new generation of fungi is propogated.
Asexual Reproduction: Sac Fungi USUALLY reproduce asexually. (1) Haploid hyphae grow above earth, producing some haploid spores. (2) The spores are dispersed. (3) When a spore reaches its destination, hyphae develop and a new generation, identical to its parent, is propogated.
All photographs acquired using google image
All diagrams and illustrations are hand drawn by Jon, Chuck and Jesslyn
Reproduction diagrams adapted from:
Info adapted from:
Biology; Concepts and Applications: Fifth Edition
All text written / website design done by Chuck Goldhaber, Jonathan Wachter and Jesslyn Jamison
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